QUANTITATIVE DETERMINATION OF CALCITE AND DOLOMITE IN PURE CARBONATES AND LIMESTONES

Abstract

SummaryCalcite and dolomite were differentiated quantitatively from calcite‐dolomite mixtures and limestones by a method based on the quantitative dissolution of calcite in pH 5.85N citrate buffer. The acidity and chelating ability of citrate favoured greatly the dissolution of calcite to that of dolomite. The method consisted of determination of citrate‐soluble Ca and Mg which, in conjunction with a Ca and Mg analysis of the residue, or a determination of total CO3 in the system, allowed calculation of the calcite and dolomite contents of the sample.Analyses of artificially prepared mixtures and limestone samples gave essentially the same calcite and dolomite contents when determined by the residue and total CO3 methods. The residue method is to be preferred because error can be reduced by determination of the actual Ca:Mg ratio of the dolomite. However, the total CO3 method would be superior for heterogeneous systems, such as soils, since dissolution of dolomite in the residue by strong acid treatment may introduce errors from the dissolution of non‐carbonate Ca and Mg minerals.